This invention relates to improvements in timed switches, more particularly timed switches of the type having a three-position selector for either manual or for automatic timed actuation.
Timed switches are well known, of the type shown in U.S. Pat. No. 3,138,674, issued June 23, 1964 to R. L. Boyles, wherein a conventional clock mechanism comprising a motor, timing gear train, and indicating hands is provided with additional means to actuate an electric switch at a selectable time. The time is selected by a manually rotatable setting gear, which is coaxially disposed and axially movable with respect to a timing gear. At a particular position of the timing gear with respect to the setting gear, the two are displaced apart from one another by mutually coacting cams to unlatch a spring biased selector arm which closes a switch.
The arrangement shown in the Boyles patent utilizes a switch contact bar, which doubles both as a switch closure member and as a cam traveler. This offers no flexibility as to easy substitution of switches of different amperage ratings, or changing from timed "ON" to timed "OFF" operation.
The Boyles patent utilized a helical spring both as a torsional and as a compressional spring biasing means. This spring, and the design of the automatic latching arm resulted in considerable frictional resistance on the drive mechanism when automatically actuating the switch. Improvements in the latter problem are seen in the timed switch disclosed in U.S. Pat. No. 3,432,625, issued Mar. 11, 1969, to S. Polonsky et al. Polonsky shows a three positioned rotatable selector included a pair of latching arms, one of which interacts with a fixed detent, and the other of which includes a projection captured within a rotatable cup-shaped detent on the setting gear in the automatic position. Axial displacement of the setting gear will unlatch the automatic latching arm. In the Polonsky patent, spring biasing of the selector to the center position is accomplished by means of a resilient conductive wire contact member passing against a flat surface on the selector shaft. Again, the integration of the switch contact members into the mechanical aspects of the timer release mechanism made it difficult to utilize switches of different ratings or functions which were commercially available.
A timed switch mechanism would be desirable which enables the use of standard microswitches of higher rating, and which utilizes relatively few components which are easy to assemble.
Accordingly, one object of the present invention is to provide improvements in a timed three-position switch.
Another object of the invention is to provide an improved timed switch, which is simple to manufacture and assemble.